Mechanical ventilators are used to assist or replace at least in part spontaneous breathing of a patient. Although significant advances have been made in ventilation therapy, it is still difficult a task to determine the level of ventilatory assist that may be required, at any given time, by a patient.
U.S. Pat. No. 8,720,441 B2 to Sinderby, issued on May 13, 2014, the full disclosure of which is incorporated by reference herein, describes how a patient's efficiency to generate an inspiratory volume without mechanical ventilatory assist and a patient's efficiency to generate an inspiratory volume with mechanical ventilatory assist are calculated and used to determine a patient-ventilator breath contribution index. This reference expresses that a patient-ventilator breath contribution is related to a relative unloading of the respiratory muscles. The relative unloading may be expressed as a reduction, in percentage, of inspiratory oesophageal pressure variations obtained through the use of mechanical ventilatory assist.
US Patent Application Publication 2001/0301482 A1 to Sinderby et al., published on Dec. 8, 2011, the full disclosure of which is incorporated by reference herein, describes a method and a system for measuring changes in inspiratory load of a patient's respiratory system during mechanical ventilation. The method and system calculate a first relation between a measured inspiratory airway pressure and a measured electrical activity of respiratory muscle, and a second relation between a measured inspiratory volume and the measured electrical activity. A load index is calculated from the first and second relations. Changes in inspiratory load are determined based on the load index.
The above references and other known techniques that provide information feedback related to a patient's respiratory system are instrumental in controlling mechanical ventilators. However, they still fail to provide readily usable ventilatory assist level information, for example a numerical value indicative of the level of ventilatory assist to be applied to a certain patient.
Therefore, there is a need for technical solutions providing ventilatory assist level information readily usable for adjusting the level of ventilatory assist to a patient.